The former Arsenal star is eagerly anticipating Tuesday's encounter and expects a difficult match at Camp Nou
The Catalans recorded a 1-1 draw at the Santiago Bernabeu in the first leg, and Fabregas is aware that los Blancos will pose a stern test in the return fixture, particularly given his side's laboured form in recent weeks.
"It’s vital to score. We cannot go into the match and wait to see what happens. In last year’s Copa del Rey Clasico we had a good result from the away leg yet we were nearly eliminated from the competition," Fabregas told Barca TV.
"Real Madrid are very dangerous and in order to go through we’ll have to play the best football we’re capable of.
"We had our chances to make it 0-2 in Madrid [in the first leg]. In the return leg we have to be as effective as possible, because they are very effective.
"We have to be on target in front of goal if we want to get to the final."
Tuesday's match at Camp Nou kicks off at 21:00CET.